(disclaimer: I wrote WTFPL v2)
I fart on your recommendation of the CC0.
Your first “reason” is totally bogus. There is no need to cover cases where it’s not possible to place stuff in the public domain, because there is no need to place stuff in the public domain. That’s a fabrication of the CC0 license and one of the reasons why the OSI does not recommend it. A license shouldn’t even mention public domain since it’s not a widely accepted concept.
Your second “reason” sounds like a matter of taste to me, especially since the CC0 goes to great lengths defining new terms such as “Commons” and “Affirmer”. If there’s a joke here, it’s the CC0, in needing more than a thousand words to basically say “do what the fuck you want”.
Moreover, here is a quote from the OSI about the CC0: “the Committee felt that approving such a license would set a dangerous precedent, and possibly even weaken patent infringement defenses available to users of software released under CC0”.
It’s also worth noting that the WTFPL predates the CC0 by nine years. Nine years to fill a non-existing void, and they couldn’t even do it properly.